const spawn = require('child_process').spawn;  
const ls = spawn('ls', ['-lh', '/usr']);  
ls.stdout.on('data', (data) => {  
  console.log(`stdout: ${data}`);  
});  
ls.stderr.on('data', (data) => {  
  console.log(`stderr: ${data}`);  
});  
ls.on('close', (code) => {  
  console.log(`child process exited with code ${code}`);  
});  
